Question

我有这个SQL语句从orders表中提取一个值（OrderID）。

"SELECT DISTINCT (MAX(OrderID)) FROM orders WHERE Username = 'hello@hello.com';

我通过PHPMyAdmin运行它，它为该用户返回一个订单ID，这完全是我想要的。但是，我试图在PHP中运行它...

"SELECT DISTINCT (MAX(OrderID)) FROM orders WHERE Username = '". $_SESSION['Username'] ."'";

我想要提取订单ID，然后我可以设置$OrderID = (the result from the select statement)，然后运行更新语句，如下所示。

$sql = "UPDATE orders SET Status = 'Failed' WHERE Status = 'Success' and OrderID = ". $OrderID ."";

如果我硬代码$OrderID = 90;它完美无缺，但我需要OrderID通过登录的人的会话来完成。

完整代码：

<?php
$url = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];

if (strpos($url,'order-failed') !== false) {
    $servername = "NULL";
    $username = "NULL";
    $password = "NULL";
    $dbname = "NULL";

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);

    // Check Connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    $query = "SELECT DISTINCT (MAX(OrderID)) FROM orders WHERE Username = '". $_SESSION['Username'] ."'";
    echo $query . "<br />";

    $OrderID = 93;
    echo $OrderID;
    echo "<br />";
    $sql = "UPDATE orders SET Status = 'Failed' WHERE Status = 'Success' and OrderID = ". $OrderID ."";
    echo $sql;

    if ($conn->query($sql) === TRUE) {
        echo "<br />Record updated successfully";
    }

    else {
        echo "<br />Error updating record: " . $conn->error;
    }

    $conn->close();
}

else {
    session_destroy();
}
?>

Answer 1

看起来这会产生同样的效果......

$sql = "
UPDATE orders 
   SET Status = 'Failed' 
 WHERE Status = 'Success'
   AND Username = '{$_SESSION['Username']}'
 ORDER 
    BY OrderID DESC 
 LIMIT 1;
    ";

...虽然明显重写它以使用预准备语句语法

Answer 2

在顶部添加会话开始

<?php
session_start();
// your code here

Answer 3

替换

echo $query . "<br />";

$OrderID = 93;
echo $OrderID;
echo "<br />";

与

$result = $conn->query($query);
$row = $result->fetch_row();
$OrderID = $row[0];

并做其他所有人说的话

http://php.net/manual/en/mysqli-result.fetch-row.php

http://php.net/manual/en/mysqli-result.fetch-array.php

http://php.net/manual/en/mysqli-result.fetch-assoc.php

Answer 4

首先，测试会话变量是否存在以及在select语句中为max（）函数指定别名可能是明智的。

> library(curl)
> h <- new_handle()
> l2<-"http://rediff.com"
> curl_download(l2,"b.txt",handle=h)
> system("lsof | grep rediff")
> l3<-"http://materialresourcing.com/tags/diy"
> curl_download(l3,"c.txt",handle=h)
> system("lsof | grep materialresourcing")
R         17936          xxxx    7u     IPv4            3559514      0t0     TCP ip-10-0-xx:40844->vps.materialresourcing.com:http (CLOSE_WAIT)
sh        18257          xxxx    7u     IPv4            3559514      0t0     TCP ip-10-0-xx:40844->vps.materialresourcing.com:http (CLOSE_WAIT)
grep      18259          xxxx    7u     IPv4            3559514      0t0     TCP ip-10-0-xx:40844->vps.materialresourcing.com:http (CLOSE_WAIT)
>

通过PHP从MySQL数据库中提取一个独特的单值

4 个答案: